Study of capping agent effect on the structural, optical and photocatalytic properties of zinc sulfide quantum dots

In this work, the effect of capping agent type on the structural, optical and photocatalytic properties of pure zinc sulfide (ZnS) quantum dots (QDs) has been investigated. ZnS QDs were prepared by a simple, fast and water based chemical precipitation method, in the presence of various capping agents including 2-mercaptoethanol, thiourea, and l-cysteine. The obtained QDs have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), and UV–visible absorption spectroscopy. The results revealed that the optical absorption band of ZnS nanostructures varied by capping agents. In the photocatalytic investigations, the prepared ZnS QDs were applied for the photodecolorization of crystal violet (CV) as a model molecule. Influence of affecting parameters on the decolorization efficiency of the capped ZnS QDs was studied and optimized. The results indicated that the prepared QDs can effectively remove different concentrations of CV dye at alkaline pH, in the presence of low concentrations of QDs. According to the photocatalytic results, the presented method can be considered as a green, quick and efficient strategy for photobleaching of organic pollutants based on the high performance photocatalytic behavior of ZnS QDs capped by different capping agents.